1. Field of the Invention
The present invention relates to an audio processing device that performs audio signal processing to a digital audio signal.
2. Description of the Related Art
In recent years, there is an audio processing device that is configured to activate so as to achieve energy saving when external equipment is connected. As the audio processing device, there is an AV receiver that performs audio signal processing such as sound field processing, D/A conversion, and amplification to a digital audio signal (for example, see JP 2015-065502 A). FIG. 11 is a block diagram illustrating configuration of a conventional AV receiver. For example, an AV receiver 101 is connected to a CD player that is external equipment by an optical digital cable. The CD player reads digital data from a CD and outputs an SPDIF signal to the AV receiver 101.
The AV receiver 101 includes a receiving circuit 103, a detection circuit 103, and a microcomputer 102. The AV receiver 101 includes a DSP (Digital Signal Processor) and so on, but description is omitted. The receiving circuit 103 receives the SPDIF signal that is output from the CD player. The detection circuit 104 detects that a digital audio signal terminal is connected and supplies a detection signal. The microcomputer 102 activates the AV receiver 101 when the detection circuit 104 supplies the detection signal.
However, it cannot be judged whether the SPDIF signal is an audio signal indicating sound or not because the SPDIF signal is a bi-phase signal. For this reason, there is a problem that although the SPDIF signal is silence, the AV receiver activates, and wasteful electric power is consumed.